What happened to Ctrl-Click in Blender 2.8?
The extrude shortcut hasn't changed, the default select button has.

The extrude shortcut is &#9096; Ctrl+ non-select mouse button, where 2.7x defaults to  RMB select, you use &#9096; Ctrl LMB to extrude, Now that 2.80 has  LMB select you use &#9096; Ctrl RMB to extrude, unless you change your selection setting.

In 2.80, &#9096; Ctrl LMB can select a different object while in edit mode. This appears to be a planned feature, it can be useful for example when adding hook modifiers that use different objects for different vertices, where the selected object is assigned to a modifier property.